1. Field of the Invention
The invention relates to a bumper arrangement enclosed by a cover and mounted on the front end or rear end of a car body of an automobile.
2. Description of the Related Art
A bumper arrangement for the front module of an automobile is known from German patent 196 11 934 C1. It is comprised of two transverse supports arranged above one another. While the upper transverse support is directly connected to upper longitudinal support beams of the car body of the automobile, impact damping members are provided between the lower longitudinal support beams of the car body and the transverse support. Furthermore, the two transverse supports are connected to one another in the area of the impact damping members via tension and compression bars that are arranged in a V-shape. The compression bars extend from the upper transverse support to portions of the impact damping members connected to the lower longitudinal support beam, while the tension bars extend from the upper transverse support to the portions of the impact damping members connected to the lower transverse support. Moreover, the tension bars which have a weaker impact resistance are provided with predetermined breaking points which have the object to allow as little load as possible to be transmitted into the upper support plane upon impact.
In the known case, the two transverse supports are supposed to form a rigid frame. In an impact situation in which the bumper arrangement impacts another vehicle from below, the upper transverse support is subjected to a load which is transmitted via the compression bars onto the relatively rigid lower support plane where it is neutralized or compensated. At the same time, a bending load is exerted onto the connecting points of the compression bars caused by the force component acting in the direction of the longitudinal vehicle axis. Because of the incorporation of the tension bars, these connecting points are relieved of load. The tension bars load substantially only the lower support plane. With such an arrangement, a front module is supposedly provided which has high stability in accidents, is repair-friendly, and provides an optimal impact behavior in situations in which the bumper arrangement impacts another vehicle from below as well as in high speed impacts.
It is an object of the present invention to provide a bumper arrangement for the front or rear end of a car body of an automobile enclosed by a cover which fulfills its function in a crash situation with low force level at low speed as well as in a crash situation with high force level at high speed and great mass.
In accordance with the present invention, this is achieved in that the bumper arrangement comprises a transverse support whose ends are connected by spacer consoles and stop plates to the longitudinal support beams of the car body and further comprises a transverse beam arranged below the transverse support which is also supported at the stop plates by means of spacer stays arranged below the spacer consoles, wherein the transverse support and/or the spacer consoles have at least over portions thereof at least two deformation areas with different force levels arranged next to one another in the longitudinal vehicle direction.
According to the invention, the transverse support, the transverse beam, the spacer consoles, and the spacer stays together are to be considered a unitary system for fulfilling the demanded requirements. In this manner, it is possible to respond in a directed manner to a respective crash situation. This is, on the one hand, a crash with low force level at low speed; this can be an impact with a minimal or great mass. On the other hand, a crash at a high force level and high speed with great mass is to be considered.
With the additional transverse beam below the transverse support it is possible to account for additional energy absorption in a front or rear crash situation. In addition to the additional energy absorption, a further positive effect of this arrangement is that an obstacle is impacted with a substantially larger surface area. This means that the type of impact is changed. Furthermore, an energy conversion onto at least two different force levels is realized. In this context, each force level is matched to a certain crash situation. In particular, it is possible without problems to design all components of the bumper arrangement in a differentiated manner with regard to function, material, and position and to optimize in this context the passive and active components in regard to vehicle safety with respect to fulfilling their function and requirements.
The deformation areas at the transverse support and/or at the spacer consoles can be designed in several ways. The material of the deformation areas can be a metal or can be a non-metallic material. Also possible is a composite construction. In this context, aluminum, steel, synthetic materials, magnesium or also foam materials can be employed. Furthermore, a hybrid design is possible.
Over all, a front or rear module is provided which can be integrated entirely into the car body of an automobile and can be exchanged, if needed, completely or partially, i.e., individual parts thereof can be replaced.
The transverse beam arranged below the transverse support can be tubular. The transverse beam can have a round, rectangular, or triangular cross-section.
Also conceivable is an embodiment in which the transverse beam has a profiled member design. The profiled member can have a hat-shaped cross-section with a bottom stay, two legs, and two flanges.
Independent of whether the transverse beam is tubular or a profiled member, steel, high strength steel, aluminum, plastic (synthetic) materials or composite materials can be used.
In order to allow further energy absorption in the area of the transverse beam, it may be expedient according to another configuration of the present invention to provide at least the surface area of the transverse beam facing the cover with a coating of an energy-absorbing material. Such a material can be, for example, a reversible or irreversible foam in the form of polyurethane (PUR), aluminum, epoxy resin (EP) etc.
When the transverse beam has a round cross-section, the coating is preferably provided over its entire circumference. In regard to other cross-sections or a transverse beam in the form of a profiled member, for example, having a hat-shaped cross-section, only the outer side of the transverse beam facing the cover is expediently coated with the energy-absorbing material.
The spacer stays arranged between the transverse beam and the stop plates are advantageously also in the form of profiled members. Preferred is, in particular, a hat-shaped cross-sectional profile. This makes it possible to provide the spacer stays with comparatively thin walls.
The spacer stays can also be embodied as hollow profiled members. Conceivable are rectangular, triangular or round cross-sections.
As has been mentioned above, the transverse support and/or the spacer consoles, at least over portions thereof, can have at least two deformation areas of different force levels, i.e., one being low and one being high, arranged next to one another in the longitudinal vehicle direction. In one embodiment the deformation areas with low force level are correlated with the rectangular, triangular, or round hollow profiled members of the spacer consoles. The deformation areas in this embodiment are formed by corrugated sidewalls of the spacer consoles. The basic design of the corrugation can be matched to the respective vehicle type.
However, in spacer consoles in the form of a hollow profiled member that can have any suitable cross-section, it is also possible to provide the deformation areas with low force level by a corresponding reduction of the wall thickness of the walls of the spacer consoles.
Furthermore, it is possible to design the deformation areas with low force level by providing penetrations or cutouts in the walls of the spacer consoles.
One embodiment according to the invention is realized in that the deformation areas with the low force level for spacer consoles having hollow profiled members of any suitable cross-section are formed by foam bodies. The force level can be adjusted in an optimal manner by the thickness of the foam body. It is possible to employ reversible or irreversible foams.
Preferably, the deformation areas of the spacer consoles with the low force level are positioned adjacent to the transverse support. Their position in the vicinity of the transverse support increases and optimizes the lateral stiffness of the spacer consoles.
However, it is also possible to position the deformation areas of the spacer consoles with the low force level adjacent to the stop plates.
The U-shaped transverse support having a bottom stay facing the cover can be provided with a longitudinal groove. This configuration is used, in particular, when the deformation area with the low force level is integrated into the spacer consoles.
In another embodiment, the deformation area with low force level is provided at the transverse support. For this purpose, the transverse support is U-shaped. Its legs point in the direction toward the cover. The legs can have flanges at their free ends. A strip-shaped foam body is inserted into the channel defined by the bottom stay and the legs and projects from the channel in the direction toward the cover. Preferably, it rests against the inner side of the cover. In this context, it is also possible to employ reversible or irreversible foam materials. The cross-sectional area of the channel can be used advantageously as a compression space.
A further embodiment suggests a tubular transverse support. In particular, a transverse support with a rectangular cross-section is used and the longitudinal axis of the cross-section extends vertically. At the longitudinal side of the transverse support facing the cover spaced apart openings or cutouts are provided. Into these openings foam blocks are inserted which rests against the inner side of the sidewall facing the sidewall provided with the cutouts or openings. The foam blocks project from the transverse support in the direction toward the cover. In particular, they rests against the inner side of the cover. Preferably, the foam blocks have a rectangular cross-section so that they are secured against rotation. Their function is fulfilled when in a crash situation the foam blocks are pressed completely into the tubular transverse support.
In yet another embodiment of the invention, the transverse support has two deformation areas with different force levels. For this purpose, the transverse support is comprised of two U-shaped profiled members. The inner U-shaped profiled member facing away from the cover has preferably two flanges projecting outwardly away from the legs in opposite directions. The outer U-shaped profiled member is connected with its legs to the inner U-shaped profiled member. Welding connections or adhesive connections can be used for this purpose, but other types of connections known to a person skilled in the art are also possible. The two bottom stays of the U-shaped profiled members are spaced from one another. The U-shaped profiled member neighboring the cover is of a weaker construction with respect to the force level, realized by means of the wall thickness and/or the material properties. In the case of an impact, this U-shaped profiled member is deformed first, elastically and/or plastically. When the impact force continues, both U-shaped profiled members together provide a resistance to the crash impact at a higher force level.
According to another embodiment of the invention, the transverse support is provided with the two adjacently positioned deformation areas of different force levels by having two U-shaped profiled members which are arranged such that their legs face one another. Advantageously, the two U-shaped profiled members have flanges at their legs by which the U-shaped profiled members are connected to one another. In this embodiment, the U-shaped profiled member adjacent to the cover is also designed to be weaker with regard to the force level by adjusting the wall thickness and/or the material properties.